Imaging device, image processing device, display control device and imaging display apparatus

ABSTRACT

A short delay time from imaging of an imaging element to displaying on a view finder is realized using a simple circuit configuration. In a live view mode, an image processing circuit performs image processing on imaging data from an image sensor, and generates image data of a display image. When processing for one line ends, progress information is output. When the image data of the display image is able to be output in synchronization with a second horizontal synchronization signal, a timing generator causes a data enable signal to be active, and supplies the image data to a data input unit according to this progress information on the other hand, when the image data is unable to be output, the timing generator causes the data enable signal to be inactive and supplies dummy data to the data input unit.

TECHNICAL FIELD

The present invention relates to an imaging device, an image processingdevice, a display control device and an imaging display apparatus thatcause a captured image to be displayed.

BACKGROUND ART

In a so-called mirror-less SLR digital camera, an image of a subject canbe confirmed through a so-called live view operation in which an imageaccording to an image signal obtained by imaging in an image sensor suchas a charge coupled device (CCD) or a complementary metal-oxidesemiconductor (CMOS) image sensor is displayed in real time on a liquidcrystal panel provided on a back surface of a housing or an electronicview finder (hereinafter, an EVF) attached to an upper portion of thehousing.

However, in this live view, a long delay occurs from imaging of asubject in the image sensor to displaying on the view finder. Therefore,it becomes difficult to cause a camera to follow a moving subject.Further, when imaging of a still image is instructed based on thedisplayed image of a subject, a difference in a timing is generatedbetween the displayed image of the subject and the image of a stillimage that is actually captured. In particular, it becomes difficult tocapture an intended still image in the case of a fast moving subject.

Therefore, a technology for shortening a delay from capture in an imagesensor of an image signal displayed on the view finder or the like hasbeen known (for example, PTL 1).

CITATION LIST Patent Literature

[PTL 1]

-   JP-A-2011-244170

SUMMARY OF INVENTION Technical Problem

In the technology described in PTL 1, a horizontal scanning period ofthe image signal is adjusted through, for example, extension of a frontporch time of the horizontal scanning period of the image signal, and adelay after imaging in the image sensor to displaying on the EVF isshortened when viewed in units of frames. In such an operation, since atiming of the horizontal synchronization signal varies, a configurationfor following the variation in the timing of the horizontalsynchronization signal to perform display control is necessary in adriving circuit of the EVE′ or the like. Therefore, a circuitconfiguration becomes complicated.

The present invention has been made in view of the above-describedcircumstances and it is an object of the present invention to realize ashort delay time from imaging of an imaging element to displaying usinga simple circuit configuration.

Solution to Problem

According to an aspect of the present invention, there is provided animaging device including: an imaging element that captures an image andoutputs an imaging signal; an image signal output unit that outputs animage signal based on the imaging signal; and a control signal outputunit that outputs a control signal indicating whether the output imagesignal is valid or invalid in synchronization with a horizontalsynchronization signal.

According to this aspect, since the control signal output unit outputsthe control signal indicating whether the output image signal is validor invalid in synchronization with the horizontal synchronizationsignal, it is possible to determine whether the image signal output fromthe image signal output unit is valid or invalid.

In the imaging device according to the above-described aspect, it ispreferable that a period of the horizontal synchronization signal isconstant, and the image signal includes an invalid image signal and avalid image signal, and either the invalid image signal or the validimage signal is output in synchronization with the horizontalsynchronization signal.

In the imaging device according to the above-described aspect, it ispreferable that the control signal output unit outputs a control signalindicating that the image signal is the valid image signal when theimage signal is able to be output in synchronization with the horizontalsynchronization signal, and outputs a control signal indicating that theimage signal is the invalid image signal when the image signal is unableto be output in synchronization with the horizontal synchronizationsignal.

According to this aspect, when the image signal is the invalid imagesignal, the display device (display unit) that receives the invalidimage signal can regard the horizontal synchronization signalsynchronized with the image signal as being a dummy and adjust avertical scanning period. Further, since it is possible to determinewhether the image signal is the valid image signal or the invalid imagesignal based on the control signal, it is possible to cause the validimage signal among image signals to be displayed on the display unit.Accordingly, when the image signal output unit outputs the invalid imagesignal as the image signal, it is possible to adjust a timing ofdisplaying on the display unit provided in a subsequent stage. Further,the image processing of which the processing time varies may be imageprocessing of which processing time necessary to obtain an image signalfor one line varies. In this case, the image processing may beprocessing in units of lines or may be processing in units of blockssuch as each of a plurality of lines, each half of one line, or eachpredetermined region. The point is that the image processing is anyimage processing as long as time required for obtaining the image signalfor one line as a processing result varies.

In the imaging device according to this aspect, it is preferable thatthe image signal output unit includes an image processing circuit whichperforms image processing of which processing time is variable on theimaging signal, and outputs progress information indicating progress ofthe image processing; and an image output circuit that determineswhether a signal obtained through the image processing of the imageprocessing circuit is able to be output as the valid image signal insynchronization with the horizontal synchronization signal based on atleast the progress information, and outputs the valid image signal whena determination condition is positive and the invalid image signal whenthe determination condition is negative. When the valid image signal isoutput as an image signal, it is necessary for at least image processingto be completed, but according to this aspect, since it can be detectedthat the image processing is completed based on the progressinformation, other conditions can be added as necessary to determinewhether the signal is able to be output.

Next, according to another aspect of the present invention, there isprovided an image processing device including: an image signal outputunit that outputs an image signal based on an imaging signal obtained bycapturing an image; and a control signal output unit that outputs acontrol signal indicating whether the output image signal is valid orinvalid in synchronization with a horizontal synchronization signal.

According to this aspect, since the control signal output unit outputsthe control signal indicating whether the output image signal is validor invalid in synchronization with the horizontal synchronizationsignal, it is possible to determine whether the image signal output fromthe image signal output unit is valid or invalid.

Next, according to still another aspect of the present invention, thereis provided a display control device including: an input unit thatinputs an image signal and a control signal indicating whether the imagesignal is valid or invalid in synchronization with a horizontalsynchronization signal; and a display control unit that performs controlto cause a valid image signal to be displayed on a display unit based onthe control signal. According to this aspect, the display control unitcan determine whether the image signal input by the input unit is avalid image signal or an invalid image signal based on the controlsignal, and cause the valid image signal among the image signals to bedisplayed on the display unit. Accordingly, it is possible to cause onlythe valid image signal to be displayed on the display device even whenthe invalid image signal is included in the image signal.

In the display control device according to the above-described aspect, aframe rate at which the display unit can perform displaying may behigher than a frame rate of an imaging signal. Thus, even when theinvalid image signal is supplied, a delay time up to displaying on thedisplay unit can be sequentially shortened and synchronization can bemade.

Next, according to still another aspect of the present invention, thereis provided an imaging display apparatus including: the imaging deviceaccording to the present invention; the display control device accordingthe present invention; and a display unit that displays an image.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of animaging display apparatus of an embodiment.

FIG. 2 is a conceptual diagram illustrating an example of a relationshipbetween image processing and progress information.

FIG. 3 is a timing chart illustrating an example of a signal suppliedfrom an image output circuit to an EVF controller during one horizontalscanning period when valid image data Dgb is output.

FIG. 4 is a timing chart illustrating an example of a signal suppliedfrom the image output circuit to the EVF controller during onehorizontal scanning period when valid image data is not output.

FIG. 5 is a block diagram illustrating a more detailed configurationexample of the EVF controller constituting the imaging displayapparatus.

FIG. 6 is a diagram illustrating an example of a value set in aregister.

FIG. 7 is a conceptual diagram illustrating a configuration example of alight receiving unit of an image sensor.

FIG. 8 is a conceptual diagram illustrating an example of an arrangementof pixels of the light receiving unit of the image sensor.

FIG. 9 is a conceptual diagram illustrating an example of a relationshipbetween a display area of a liquid crystal panel and a driving timing ina vertical direction and a horizontal direction.

FIG. 10 is a flowchart illustrating an example of a process ofoutputting an image signal in an image output circuit.

FIG. 11 is a timing chart illustrating an example of a change in avertical scanning period of a display image due to insertion of dummydata in the image output circuit.

FIG. 12 is a timing chart illustrating an example of image processing ofeach line of image data of a display image in the vertical scanningperiod and an output process of the image data.

FIG. 13 is a flowchart illustrating an example of a driving operation ofan EVF in the EVF controller.

FIG. 14 is a conceptual diagram conceptually illustrating an example ofan operation from output of an imaging signal of an imaging unit todriving of the EVF.

FIG. 15 is a block diagram illustrating a configuration example of anEVF controller constituting an imaging display apparatus according to avariant example.

FIG. 16 is a diagram illustrating an example of an image signal (imagedata) for one pixel of a display image in an LVDS signal.

FIG. 17 is a diagram illustrating another example of an image signal(image data) for one pixel of a display image in an LVDS signal.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of an imaging device of the presentinvention will be described in detail. Further, these embodiments areillustrative, and accordingly, content of the present invention shouldnot be restrictively construed.

Further, a case in which, for example, a liquid crystal panel that is anexample of an electro-optic device is used as a display element of adisplay unit will be described below in each embodiment.

First Embodiment Configuration of Imaging Display Apparatus

FIG. 1 is a block diagram illustrating a configuration of an imagingdisplay apparatus 1 of this embodiment.

This imaging display apparatus 1 includes an imaging unit 10 thatoutputs imaging data Ds [imaging signal] obtained by imaging a subjectin synchronization with a first horizontal synchronization signalSHsync, an image processing circuit 20 that performs image processing onthe imaging data Ds to generate image data Dga, an image output circuit30 that reads the image data Dga from the image processing circuit 20 insynchronization with a second horizontal synchronization signal DHsyncand outputs image data Dgb (D00 to D23) [image signal], an EVFcontroller 40 that controls an operation of an EVF 50 according to theimage data Dgb, the EVF 50 having a display element such as a liquidcrystal panel, an operation input unit 60 that inputs, for example, aninstruction to change a setting and perform photography, and a controlunit 70 that controls an entire operation of the imaging displayapparatus 1.

This imaging display apparatus 1 is a so-called mirror-less digitalcamera, in which a so-called live view operation in which an imageobtained through imaging of the imaging unit 10 is displayed on the EVF50 in real time, as well as a photography operation of reading theimaging data Ds of all pixels of an image sensor 12, performing aprocess such as a filtering process, and storing the data in a memory 29for still image storage can be performed.

Then, the imaging unit 10 includes an imaging optical system 11 thatforms an image of the subject, the image sensor 12 thatline-sequentially scans signals from light receiving elements arrangedin a matrix form and outputs the imaging data Ds according to the imageof the subject, and a timing generator (TG) 13 that outputs varioustiming signals to the image sensor 12. The timing generator 13 generatesa first vertical synchronization signal SVsync, a first horizontalsynchronization signal SHsync, and a first dot clock SCLK, and outputsthe signals to the image sensor 12. Further, the first verticalsynchronization signal SVsync, the first horizontal synchronizationsignal SHsync, and the first dot clock SCLK may be output to the imageprocessing circuit 20.

The image processing circuit 20 includes a line buffer 21 thattemporarily stores the imaging data Ds, an image interpolationprocessing unit 22 that performs an interpolation process on the imagingdata Ds stored in the line buffer 21, a color reproduction processingunit 23 that performs a color reproduction process on the interpolatedimaging data Ds, a filter processing unit 24 that performs a filteringprocess on the imaging data Ds subjected to the color reproduction, agamma processing unit 25 that performs gamma processing on the imagingdata Ds subjected to the filtering process, a line buffer 26 thattemporarily stores the imaging data Ds subjected to the gammaprocessing, a resizing processing unit 27 that performs a resizingprocess of adjusting a size on the imaging data Ds stored in the linebuffer, and a VRAM/line buffer 28 that temporarily holds the imagingdata Ds subjected to the resizing process as display image data Dga.

When processing of the image data Dga for one line is completed and theimage data is able to be output, this VRAM/line buffer 28 outputs awriting completion signal when writing for one line of the display imageends, but this signal is used as progress information P for convenience.In this example, a pulse at a high level indicating “the image data isable to be output” is output as the progress information P. Since thispulse is output each time the processing of one line is completed, thenumber of pulses is counted from the start of a frame (a falling edge ofa second vertical synchronization signal DVsync to be described below),and thus, a line of which the image data Dga is able to be output can berecognized.

If an image processing time of all lines is constant, processing of theimage data Dg for one line is completed in a constant period, and thus,the progress information P is unnecessary. However, in the resizingprocess of performing adjustment of the size, the filtering process, orthe like, a processing time required for generation of the image dataDga of the display image may be different between lines of the displayimage according to an algorithm (processing method). Therefore, in thisembodiment, the progress information P is generated so that the imageoutput circuit 30 of a subsequent stage can detect that the imageprocessing circuit 20 becomes able to output the image data Dga for oneline.

FIG. 2 illustrates an example of a relationship between image processingof first to sixth lines and the progress information P. In FIG. 2, ashaded part indicates time required for image processing of one line. Inthis example, an image processing time required for generation of theimage data Dga of the first to third and fifth lines is Ta, and an imageprocessing time required for generation of the image data Dga of thefourth and sixth lines is Tb. Further, the image processing time Tb islonger than the image processing time Ta. When the time required forimage processing differs from line to line in this way, a pulse intervalof the progress information P varies according to the image processingtime.

In this example, respective pulses p1 to p6 are generated at time pointst1 to t6 at which the image processing of the first to sixth lines ends.Here, an interval between the pulse p1 and the pulse p2 and an intervalbetween the pulse p2 and the pulse p3 are the same. However, the time Tbrequired for image processing of the fourth line is longer than theimage processing time Ta. Therefore, the interval between the pulse p4generated at the time point t4 and the pulse p3 is longer than aninterval between the pulse p2 and the pulse p3.

The image output circuit 30 of a subsequent stage can detect thatpreparation for output of the image data Dga of a certain line iscompleted by referring to this progress information P. Also, when thereis a reading request from the image output circuit 30, the VRAM/linebuffer 28 outputs the image data Dga for one line to the data outputcircuit 30.

The image output circuit 30 illustrated in FIG. 1 includes a data outputcontrol unit 31 that controls output of image data Dgb (D00 to D23) tothe EVF controller 40, a serial interface (I/F) 33 that transmits, forexample, a setting parameter of a register 43 a of the EVF controller40, and a timing generator 35 that generates various timing signals.This timing generator 35 generates a second vertical synchronizationsignal DVsync, a second horizontal synchronization signal DHsync, asecond dot clock DCLK, and a data enable signal DE [control signal].Here, the second dot clock DCLK is not in synchronization with the firstdot clock SCLK described above. Therefore, the timing generator 35 canbe configured without using a PLL circuit or a frequency divider circuitnecessary for synchronization.

The data enable signal DE is a signal that becomes active (in thisexample, at a high level) during a period in which valid image data Dgb(D00 to D23) is output and becomes inactive (in this example, at a lowlevel) in other periods.

When the following conditions are satisfied, the timing generator 35causes the data enable signal DE of an n-th line to be active.

First, it is necessary for reading of the imaging data Ds necessary togenerate the n-th line from the image sensor 12 to be completed. Whenconversion of the number of lines in the resizing process is executed,for example, if the n-th line of the EVF 50 corresponds to an m-th lineof the image sensor 12, it is necessary for the imaging data Ds of them-th line to be read from the image sensor 12 to the image processingcircuit 20 (first condition).

Second, it is necessary for generation of the image data Dga of the n-thline to be displayed on the EVF 50 to be completed (second condition).

Third, it is necessary for the preparation of a display timing to becompleted in the n-th line. Specifically, it is necessary for a periodto be a horizontal display active period (horizontal valid image period)HDISP in which the image data Dgb becomes valid (see FIG. 3) during 1horizontal scanning period 1H (third condition).

It is necessary for the first condition to be satisfied in order tocomplete the generation of the image data Dga of the n-th line, which isthe second condition. Also, it can be identified whether the secondcondition is satisfied based on the progress information P. However,even when the progress information P becomes active for the n-th line,this is a necessary condition, and the data enable signal DE does notbecome active with only this condition. That is, the timing generator 35determines whether the n-th line to be displayed subsequently to the(n−1)-th line that is being currently output is able to be output whilemonitoring the progress information P, controls the data output controlunit 31 to read the image data Dga of the n-th line from the VRAM/linebuffer 28, issues the second horizontal synchronization signal DHsync,and causes the data enable signal DE to be active to output the imagedata Dgb of the n-th line to the EVF controller 40.

FIG. 3 is a timing chart illustrating a relationship between the dataenable signal DE and the image data Dgb during the 1 horizontal scanningperiod 1H in which the data enable signal DE becomes active. The 1horizontal scanning period 1H includes a horizontal synchronizationperiod HS in which the second horizontal scanning signal DHsync becomesactive (at a low level), a horizontal back porch period HBP, ahorizontal display active period HDISP, and a horizontal front porchperiod HFP, as illustrated in FIG. 3. The horizontal display activeperiod HDISP is a period for outputting the valid image data Dgb, thedata enable signal DE becomes active during the horizontal displayactive period HDISP, and the valid image data Dgb is output from thedata output control unit 31 to the EVF controller 40. Meanwhile, thedata enable signal DE becomes inactive (at a low level) during thehorizontal synchronization period HS, the horizontal back porch periodHBP, and the horizontal front porch period HFP other than the horizontaldisplay active period HDISP, and invalid image data Dgb is output duringthese periods. The EVF controller 40 fetches the image data Dgb during aperiod in which the data enable signal DE becomes active and does notfetch the image data Dgb during a period in which the data enable signalDE becomes inactive.

Here, the number of second dot clocks DCLK during the horizontalsynchronization period HS, the horizontal back porch period HBP, and thehorizontal front porch period HFP is determined in advance. Thecompletion of the preparation of the display timing, which is the thirdcondition described above, means that the 1 horizontal scanning period1H starts and a time point tx at which the horizontal back porch periodHBP ends arrives.

Further, a rising timing and a falling timing of the data enable signalDE are synchronized with a falling edge of the second dot clock DCLK.Therefore, when the EVF controller 40 latches the image data Dgb at arising timing of the second dot clock DCLK, a time margin can be held.

FIG. 4 is a timing chart illustrating a relationship between the dataenable signal DE and the image data Dgb during the 1 horizontal scanningperiod 1H when the data enable signal DE becomes inactive. Asillustrated in FIG. 4, since the data enable signal DE becomes alwaysinactive, all pieces of image data Dgb become invalid. In this case, inthe EVF controller 40, the image data Dgb of the corresponding line isnot fetched.

In the above-described description, the units of the image processingcircuit 20 and the image output circuit 30 except for the timinggenerator 35 function as an image signal output unit that outputs theimage signal Dgb based on the imaging signal Ds, and the timinggenerator 35 functions as a control signal output unit that outputs theenable signal DE (control signal) indicating whether the output imagesignal Dgb is valid or invalid in synchronization with the horizontalsynchronization signal DHsync.

Referring back to FIG. 1, the EVF controller 40 supplies various timingsignals and image data Dgc to the EVF 50. The EVF 50 includes a liquidcrystal panel 51 in which pixels are arranged in positions in whichscanning lines and data lines intersect in a matrix form, a scanningline selection unit 52 that selects the scanning line of the liquidcrystal panel 51, a data line driving unit 53 that drives the datalines, and an eyepiece optical system 55 that enlarges an image of theliquid crystal panel 51 so that the image is observable.

FIG. 5 is a block diagram illustrating a detailed configuration of theEVF controller 40 and the EVF 50. The EVF controller 40 includes a datainput unit 41 that inputs the image data Dgb from the data outputcontrol unit 31, a counter 42 that counts the number of lines of thevalid image data according to the data enable signal DE and the secondhorizontal synchronization signal DHsync described above, a timinggeneration unit 43 that generates a driving timing of the EVF 50, a dataoutput unit 44 that outputs the image data to the EVF 50, and a serialI/F 45 that performs, for example, reception of a command from theserial I/F 33, as illustrated in FIG. 5.

The timing generation unit 43 includes a register 43 a, and a value ofthe register 43 a is set according to, for example, a command from theimage output circuit 30 received via the serial I/F 45. Specifically,the serial I/F 33 and the serial I/F 45 perform communication accordingto a protocol such as an Inter-Integrated Circuit (I2C) or a SerialPeripheral Interface (SPI). The serial I/F 33 transmits a commandcontaining a setting parameter to the data output unit 44. The dataoutput unit 44 sets the value of the register 43 a according to thereceived setting parameter.

The setting parameters (setting items) set in the register 43 a include,for example, a 1 horizontal synchronization period of the liquid crystalpanel 51 (an interval 1H of the second horizontal synchronization signalDHsync in FIG. 9), a horizontal back porch period (HBP in FIG. 9), thenumber of horizontal pixels (the number of pixels in a horizontaldirection of the display area corresponding to HDISP in FIG. 9), ahorizontal front porch period (HFP in FIG. 9), a 1 verticalsynchronization period (an interval 1V of the vertical synchronizationsignal DVsync in FIG. 9), a vertical back porch period (VBP in FIG. 9),the number of vertical pixels (the number of lines of the display areacorresponding to VDISP in FIG. 9), and a vertical front porch period(VFP in FIG. 9), as illustrated in FIG. 6.

Thus, since the timing based on a specification of the EVF 50 can be setfrom the image output circuit 30, it is not necessary to change the EVFcontroller 40 even when the specification of the EVF 50 such as theliquid crystal panel 51 having a different size or a frame rate ischanged. Thus, it is possible to improve versatility of the system.

Incidentally, more specifically, the above-described image sensor 12 caninclude a CMOS image sensor having about 18 million pixels of 5400*3600pixels (a used pixel area: 5280*3520 pixels), for example, asillustrated in FIG. 7. This image sensor 12 becomes able to output theimaging data Ds, for example, at a frame rate of 120 Hz through, forexample, decimation of the pixels of the line to be output in the liveview mode in which a live view operation is performed. Specifically, thepixel of the image sensor 12 is configured in a manner in which lightreceiving units that receive R, G, and B light beams are arranged in astaggered shape (Bayer array), for example, as illustrated in FIG. 8. Inthe live view mode, the image sensor 12 sets, for example, the outputlines to ⅕, and outputs an average for three pixels in a horizontaldirection. Accordingly, the number of pixels in the image data Dssupplied from the image sensor 12 to the image processing circuit 20becomes 1800*720 (the number of used pixels: 1760*704). Further, in thelive view mode, a timing of the first vertical synchronization signalSVsync, the first horizontal synchronization signal SHsync, the firstdot clock SCLK or the like generated by the timing generator 13 dependson this frame rate and the number of pixels.

Further, more specifically, the liquid crystal panel 51 can include adisplay element such as a liquid crystal (LCD) panel having a displayarea of 1024*768 pixels (a total number of lines N=768), for example, asillustrated in FIG. 9. Further, FIG. 5 conceptually illustrates arelationship between the display area of the liquid crystal panel 51 andsignals such as the second vertical synchronization signal DVsync, thesecond horizontal synchronization signal DHsync, the data enable signalDE, and the dot clock DCLK used for control of the liquid crystal panel51. This liquid crystal panel 51 becomes able to display one frame in aperiod shorter than a frame period of the image sensor 12. Specifically,this liquid crystal panel 51 can display, for example, an imageaccording to the image data Dgc at a frame rate (1/frame period) ofabout 160 Hz, which is a maximum rate.

Thus, in the imaging display apparatus 1, since a period of one framethat can be displayed on the EVF 50 is shorter than a period of oneframe of the imaging unit 10, the output of the imaging data Ds from theimaging unit 10 and image processing in the image processing circuit 20are not performed in time even when the output of the image data Dga fordisplaying is performed at a timing of the EVF 50. Therefore, in thisimaging display apparatus 1, in the live view mode, the output timing ofthe image data Dgb from the image output circuit 30 is adjustedaccording to the output of the image data Dga from the image processingcircuit 20 so that the display of the EVF 50 follows the output timingof the imaging data Ds from the imaging unit 10, as will be describedbelow.

Further, when an image according to the imaging data Ds (for example,for 1760*704 pixels) from the image sensor 12 is displayed on the liquidcrystal panel 51 (for example, for 1024*682 pixels other than a displayarea [On Screen Display (OSD) area] of photography conditions or thelike), it is necessary to perform, for example, adjustment of the size(resizing) using the above-described resizing processing unit 27according to a difference in the number of pixels. The processing timerequired for generation of the image data of the display image may bedifferent between the lines of the display image according to analgorithm for this resizing processing (processing method).

Further, when a lens distortion correction process or a filteringprocess is performed, the processing time necessary for generation ofthe display image data may be different between the lines according to atype of process. Therefore, time required for image processing in theimage processing circuit 20 may be different between the lines of thedisplay image. That is, a timing at which the generated image data Dgaof the display image becomes able to be output may be different betweenthe lines. Therefore, when the image data of the display image is outputat a fixed timing at which a safety factor is expected at a maximumamount of variation of the timing at which the image data of the displayimage becomes able to be output, a delay time from imaging of the imagesensor 12 to displaying on the liquid crystal panel 51 increases.

Therefore, in this imaging display apparatus 1, an output timing of theimage data of the display image from the image output circuit 30 isadjusted in units of horizontal scanning periods (the period of thehorizontal synchronization signal) of the EVF 50, such that a state inwhich a delay from imaging of the image sensor 12 to displaying on theliquid crystal panel 51 is minimized is kept in response to the timingat which the image data of the display image becomes able to be outputfrom the image processing circuit 20.

<Operation>

Next, an operation of the above-described imaging display apparatus 1will be described. The imaging display apparatus 1 operates at least ina photography mode and a live view mode. When a user operates theoperation input unit 60 to instruct capture of a still image, a mode isshifted to the photography mode. In the photography mode, the imageprocessing circuit 20 reads the imaging data Ds of all pixels of theimage sensor 12, performs a process such as a filtering process, andstores the resultant data in the memory 29 for still image storage. Onthe other hand, when the user operates the operation input unit 60 toselect the live view mode, the imaging display apparatus 1 executes thelive view operation in which the imaging data Ds obtained throughimaging of the image sensor 12 is displayed on the liquid crystal panel51 in real time, as described above.

In the live view mode, the image processing circuit 20 performs aprocess, such as conversion of the number of pixels according to adifference with the number of pixels of the liquid crystal panel 51, togenerate the image data Dga of the display image, and records the imagedata Dga in the VRAM/line buffer 28. The VRAM/line buffer 28 outputs awriting completion signal when writing of one line of the display imageends, but uses this signal as the progress information P forconvenience. The timing generator 35 generates timing signals such as asecond vertical synchronization signal DVsync, a second horizontalsynchronization signal DHsync, and a data enable signal DE according tothe progress information P. The data output control unit 31 reads, forevery line, the image data Dga of the display image recorded in theVRAM/line buffer 28 to supply the image data Dga to the EVF controller40 according to the timing signals generated by the timing generator 35.The EVF controller 40 drives the liquid crystal panel 51 according tothe image data Dgb supplied from the data output control unit 31 anddisplays an image.

FIG. 10 is a flowchart illustrating an operation of the image processingcircuit 30 and the control unit 70 related to the live view mode. Whenthe user operates the operation input unit 60 to select the live viewmode, an initial setting process is executed (S1). In the initialsetting process, the control unit 70 controls the image sensor 12 tooutput the imaging data Ds corresponding to the live view display.Accordingly, live view output is executed through a decimation readingoperation most suitable for the live view mode from the image sensor 12.Further, in the initial setting process, the image processing circuit 30transmits a setting parameter to the EVF controller 40. Accordingly, thesetting parameter is set in the register 43 a of the EVF controller 40.In the initial setting process, setting of the EVF controller 40 for alive view operation and a series of preparations for live view displayof the EVF 50 are performed, and a series of preparations for displayingof a live view image fetched from the image sensor 12 is completed.Further, when the live view mode is selected in an initial state of thepower supply, the initial setting process after power supply may beexecuted.

Then, the data output control unit 31 of the image output circuit 30causes the image data Dgb to be invalid in the vertical front porchperiod VFP, the vertical synchronization period VS, and the verticalback porch period VBP. Specifically, the image data Dgb becomes “0”, anddummy data is output from the data output control unit 31 (S2). Further,the timing generator 35 outputs the second horizontal synchronizationsignal DHsync during the vertical front porch period VFP, the verticalsynchronization period VS, and the vertical back porch period VBP, andcauses the second vertical synchronization signal DVsync to be activeduring the vertical synchronization period VS (S2).

Then, when the second vertical synchronization signal DVsync becomesactive, the data output control unit 31 resets an internal counter (n)(S3), and waits until a timing at which a next second horizontalsynchronization signal DHsync becomes active arrives (S4). When thetiming at which the next second horizontal synchronization signal DHsyncbecomes active arrives, the timing generator 35 determines whether thevalid image data Dgb can be output from the data output control unit 31to the EVF controller 40 (S5). Specifically, a determination is made asto whether the first and second conditions described above aresatisfied. That is, when the image data Dgb to be output nextcorresponds to the n-th line, a determination is made as to whetherreading of the imaging data Ds necessary to generate the n-th line fromthe image sensor 12 is completed (first condition), and the image dataDga of the n-th line is recorded in the VRAM/line buffer 28 (secondcondition).

In step S5, when the n-th line of the image data Dgb of the displayimage can be output, the timing generator 35, for example, causes thedata enable signal DE to be active (at a high level) during thehorizontal display active period HDISP in which the valid image data Dgbis output, as illustrated in FIG. 3 (S6). Further, the data outputcontrol unit 31 reads the image data Dga of the display image for oneline from the VRAM/line buffer 28 in synchronization with the dot clockDCLK, supplies the image data Dgb to the data input unit 41 of the EVFcontroller 40 (S7), and then causes the data enable signal DE to beinactive (at a low level) after the output of the valid image data Dgbfor one line ends (S8).

Then, the timing generator 35 confirms whether the output of the imagedata Dgb of all lines (N lines) in one frame of the display image endsbased on the value of the above-described counter (n) (S11), and returnsto the above-described step S2 to start the process for the image dataDgb of the display image of the next frame when the output ends. Whenthe process ends, the timing generator 35 increases the value of thecounter (n) (S12) and waits for a timing of the next second horizontalsynchronization signal DHsync (S4).

The second vertical synchronization signal DVsync, the second horizontalsynchronization signal DHsync, and the data enable signal DE for oneframe illustrated in FIG. 11, for example, are obtained by executingsuch a process. FIG. 11(A) is a case in which the image data Dgb of allthe lines in one frame of the display image can be output insynchronization with the second horizontal synchronization signal DHsyncof the EVF 50, and the determination condition of step S5 describedabove is satisfied for all the lines in one frame. In this case, in theentire horizontal scanning period of the vertical display active periodVDISP, the image output circuit 30 outputs the valid image data Dgb, andthus, a dummy DHsync period is not inserted. Meanwhile, FIG. 11(B)illustrates a case in which the determination condition of step S5described above is not satisfied for some lines in one frame. In thiscase, the image output circuit 30 outputs invalid image data Dgb (dummydata) in the horizontal scanning period in a part of the verticaldisplay active period VDISP. That is, when it is determined in step S5that the valid image data Dgb cannot be output, the data enable signalDE becomes inactive in the line. Hereinafter, the horizontal scanningperiod in which the invalid image data Dgb (dummy data) is output in thevertical display active period VDISP is referred to as a dummy DHsyncperiod.

In the example illustrated in FIG. 11(B), the data enable signal DEbecomes inactive as a result of the valid image data Dgb beingdetermined to be unable to be output in periods Tc and Td. These periodscorrespond to the dummy DHsync period. Accordingly, the vertical displayactive period VDISP of one frame is longer by a period in which thedummy DHsync period is inserted in comparison with FIG. 11(A). Thus, alength of the vertical display active period VDISP of one frame isadjusted in units of horizontal scanning periods. Also, the valid imagedata Dgb adjusted to a timing at which the data is able to be output canbe supplied from the image output circuit 30 to the EVF controller 40.The display can be performed in synchronization with a timing of theimaging data Ds from the image sensor 12 (synchronization with precisionin units of horizontal scanning periods) by driving the EVF 50 accordingto the image data Dgb of the display image subjected to timingadjustment. Further, as described above, it is possible to minimize theinsertion of the dummy DHsync period and minimize a delay (phasedifference) from the output of the imaging data Ds from the image sensor12 to displaying on the liquid crystal panel 51.

FIG. 12 is a diagram illustrating a process in which the image data Dgbof the display image output from the image output circuit 30 to the EVFcontroller 40 is synchronized with the imaging data Ds from the imagesensor 12 through the timing adjustment as described above. FIG. 12illustrates a case in which a frame rate of the imaging data Ds of theimage sensor 12 is 120 FPS [frame/second] (a frame period of 8.33 mS),and the frame rate of the image data Dgb that can be displayed on theEVF 50 is 160 FPS (a frame period of 6.25 mS).

Further, data enable signal DE′ illustrated in FIG. 12 is obtained byroughly catching the data enable signal DE in the 1 vertical scanningperiod. That is, strictly, a part shown by hatching the data enablesignal DE′ is not always at a high level, but becomes a high levelduring a horizontal display active period HDISP in the 1 horizontalscanning period 1H, as illustrated in FIG. 11.

As illustrated in FIG. 12, imaging data Ds [1] output from the imagesensor 12 ends at time point t10, whereas image data Dgb[1] ends at atime point tn. In this case, a delay time delta T1 (phase difference)between the imaging data Ds [1] and the image data Dgb[1] is relativelylong. Here, the long delay time delta T1 means that there is enough timefrom the end of the image processing in the image processing circuit 20to the start of the output of the image data Dgb of the display image inthe image output circuit 30. When there is enough time in this way, thedummy DHsync period is not inserted.

In this example, since the EVF display period (6.25 ms) is shorter thanthe sensor output period (8.33 ms), a delay time delta T2 from a timepoint t20 at which output of imaging data Ds [2] of a next frame ends toa time point t21 at which output of image data Dgb[2] of the displayimage corresponding to the frame from the image output circuit 30 endsis shorter than delta T1. Thus, when the adjustment of the output timingprogresses, the delay time is shortened. However, the image data Dgb ofthe display image in the image processing circuit 20 is not generated intime in a step in which the delay time is shortened to some extent.Thus, in the image output circuit 30, a line of the image data Dgb ofthe display image that cannot be output in synchronization with thesecond horizontal synchronization signal DHsync is generated, and thedummy DHsync period is inserted (for example, image data Dgb[3] in FIG.12). As a result, a minimum dummy DHsync period is inserted until theline becomes able to be output, the vertical display active period VDISPof the frame is extended, and the adjustment of the output timingprogresses. Finally, the delay time converges on a constant delay timedelta Tmin that is a minimum delay (minimum phase difference) and isstabilized, and the output timing of the image data from the imageoutput circuit 30 is synchronized with the output timing of the imagingsignal from the image sensor 12 (for example, after image data Dgb[3] inFIG. 12).

In such a synchronized state, the adjustment of the output timing isperformed through the insertion of the dummy DHsync period, and thus,the delay time delta Tmin is likely to vary in a period of the secondhorizontal synchronization signal DHsync generated by the timinggenerator 35. However, as described above, a determination is made as towhether the output synchronized with the second horizontalsynchronization signal DHsync for each line of the image data Dgb of thedisplay image is possible (step S5 illustrated in FIG. 10), and theinsertion of the dummy DHsync period is a minimum period until theoutput of the image data Dgb of the line is possible. Therefore, in thesynchronized state, adjustment to the minimum delay time delta Tminaccording to, for example, a situation of the image processing in theimage processing circuit 20 is performed. That is, in this imagingdisplay apparatus 1, the delay (phase difference) from the output of theimaging data Ds from the image sensor 12 to the displaying on the liquidcrystal panel 51 is minimized. Therefore, in this imaging displayapparatus 1, it is possible to perform the display of the EVF 50synchronized with the output timing of the imaging data Ds from theimage sensor 12 with a minimized delay time.

Then, an operation related to the live view mode of the EVF controller40 will be described. Processing content in the live view mode executedby the EVF controller 40 is illustrated in FIG. 13. First, prior tostart of the operation in the live view mode, the EVF controller 40determines whether a command (for example, a setting parameter includinga variable name and a value of the register) from the image outputcircuit 30 supplied via the serial I/F 45 is received (S21), and setsthe value of the register 43 a according to the command from the imageoutput circuit 30 when the command is received (S22).

Then, the timing generation unit 43 determines whether the secondvertical synchronization signal DVsync supplied from the image outputcircuit 30 becomes active (S23). If the second vertical synchronizationsignal DVsync becomes active, the timing generation unit 43 resets acount value of the counter 42 (S24). Then, the data input unit 41determines whether the second horizontal synchronization signal DHsyncis active (S25). When the second horizontal synchronization signalDHsync is active, the data input unit 41 determines whether the dataenable signal DE supplied from the data output control unit 31 is active(S26).

If the data enable signal DE is active, the data input unit 41 fetchesthe image data Dgb of the display image from the data output controlunit 31 for one line (S27). In this case, the counter 42 increments thecount value VC (S28). Further, the timing generation unit 43 causes thescanning line selection unit 52 to select a line (scanning line)corresponding to the count value VC, and causes the data output unit 44to supply the image data for one line fetched by the data input unit 41to the data line driving unit 53. The data line driving unit 53 writesthe supplied image data to a pixel of the scanning line selected by thetiming generation unit 43 via the data line. Accordingly, the image ofthe selected line is displayed on the liquid crystal panel 51.

Then, the timing generation unit 43 determines whether the count valueVC of the counter 42 reaches RV (“the number of vertical pixels (thenumber of valid lines)” set in the register 43 a) (S29). When the countvalue VC is equal to the valid line number RV, the reception of theimage data Dgb of all lines in one frame ends, and thus, the data inputunit 41 returns to step S23 to wait for the second verticalsynchronization signal DVsync of the next frame. When the count value VCis not equal to the valid line number RV, the reception of the imagedata Dgb of all lines in one frame does not end, and thus, the datainput unit 41 returns to step S25 to wait for the second horizontalsynchronization signal DHsync to be active.

Further, in step S26 described above, when the data enable signal DE isinactive, the image data Dgb from the data output control unit 31 isdummy data (invalid data), and thus, the image data Dgb is not fetchedand the process returns to step S25 to wait for the second horizontalsynchronization signal DHsync to be active.

In the above-described operation, the EVF controller 40 can controldisplaying on the liquid crystal panel 51 based on the image data Dgb ofthe display image during a period in which the data enable signal DE isactive, among the image data Dgb supplied from the image output circuit30.

FIG. 14 is a conceptual diagram schematically illustrating a timing upto the output of the imaging data Ds from the above-described imagesensor 12, the output of the image data Dgb of the display image fromthe image output circuit 30, and the displaying on the EVF 50 for framesfor which operation states are different, and corresponds to FIG. 12described above. Since a delay time delta T1 is relatively long for theimaging data Ds [1] output from the image sensor 12, there is enoughtime for processing in the image output circuit 30. Therefore, the imagedata Dgb [1] is generated without the dummy DHsync period beinginserted. A delay time delta T2 of a next frame being shorter than thedelay time delta T1 is because the frame rate of the EVF 50 is shorterthan the frame rate of the image sensor 12. In the next frame, the delaytime is further shortened and becomes a minimum delay time delta Tmin,but processing in the image processing circuit 20 is not performed intime, and a dummy DHsync period is inserted. As a result, image data Dg[3] includes invalid data, and valid data becomes intermittent. Theoutput of the image data Dgb of the display image from the image outputcircuit 30 may become intermittent in units of horizontal scanningperiods (an interval of the second horizontal synchronization signalDHsync) according to the progress information P from the above-describedimage processing circuit 20. In this case, the displaying on the EVE′ 50is intermittent in units of horizontal scanning periods, as well. Thatis, the driving timing of each line in one frame in the EVF 50 slightlyvaries in units of horizontal scanning periods (the interval of thehorizontal synchronization signal), but this variation is not recognizedby a person since the variation is sufficiently smaller than the displayperiod (vertical scanning period) of one frame.

Effects

As described above, in this imaging display apparatus 1, the imageoutput circuit 30 determines whether one line of the image data Dgb ofthe display image is able to be output in synchronization with thesecond horizontal synchronization signal DHsync according to theprogress information P from the image processing circuit 20, outputs theimage data Dgb of the display image for one line to the EVF controller40 in synchronization with the second horizontal synchronization signalDHsync when the line is able to be output, and outputs the dummy datawhen the line is unable to be output, such that the timing at which theimage data Dgb of the display image is output can be adjusted in unitsof horizontal scanning periods. The output timing of the image data Dgbof the display image output from the image output circuit 30 can besynchronized with the output timing of the imaging data Ds from theimage sensor 12 by performing such timing adjustment. In this case, thesynchronization is performed with precision in units of horizontalscanning periods.

Further, for the above-described progress information P, the pulse at ahigh level is output at a timing at which image processing for theimaging data Ds from the image sensor 12 is performed, the generationfor one line of the image data Dga of the display image ends, and thewriting to the VRAM/line buffer 28 ends. The image data Dgb of thedisplay image can be output with a minimum delay time by adjusting theoutput timing of the image data Dgb of the display image from the imageoutput circuit 30 according to such progress information P. Therefore,in this imaging display apparatus 1, the image data Dgb for the displayimage for which an increase in the delay time is suppressed can beoutput in synchronization with the output timing of the imaging data Dsfrom the image sensor 12. As a result, in this imaging display apparatus1, the displaying of the image on the liquid crystal panel 51 issynchronized with the output timing of the imaging data Ds from theimage sensor 12, and the delay time up to displaying on the liquidcrystal panel 51 is minimized (in units of horizontal scanning periods).

Here, in order to cause the display of the display image on the liquidcrystal panel 51 to be synchronized with the output timing of theimaging data Ds of the image sensor 12, adjustment of the length of thehorizontal scanning period in units of dot clock periods on the liquidcrystal panel 51 side is performed according to the timing at which theimage data Dgb of the display image becomes able to be output and, as aresult, timing adjustment of the vertical scanning period is considered.When such timing adjustment is performed, a circuit capable of followingvariation in the horizontal scanning period (variation in the timing ofthe horizontal synchronization signal) is necessary on the EVF 50 side,and thus, a configuration of the circuit is complicated.

On the other hand, in this imaging display apparatus 1, since the timingadjustment is performed in units of horizontal scanning periods on theliquid crystal panel 51 side, and, as a result, the timing adjustment ofthe vertical scanning period is performed, the horizontalsynchronization signal on the liquid crystal panel 51 side is output ata constant timing. The circuit following such a horizontalsynchronization signal may be able to follow the horizontalsynchronization signal at the same degree as when the image data of thedisplay image is supplied at a constant interval of the horizontalsynchronization signal at a constant frame rate. Therefore, in thisimaging display apparatus 1, it is necessary to add a counter thatcounts the number of lines of the valid image data Dgb in the verticalscanning period based on the above-described data enable signal DE, butthis configuration is not complicated in comparison with the case inwhich the timing is changed in units of dot clock units on the liquidcrystal panel 51 side. Therefore, in this imaging display apparatus 1,shortening of the delay time from imaging in the image sensor 12 todisplaying on liquid crystal panel 51 can be realized by a simplecircuit configuration.

Variant Example

The present invention is not limited to the respective embodimentsdescribed above and various variant examples to be described below arepossible. Further, each variant example may be an appropriatecombination of variant examples or may be an appropriate combination ofthe above-described embodiments.

(1) While the example of the liquid crystal panel has been described asan example of the liquid crystal panel 51 in the above-describeddescription, the present invention can also be applied to a case inwhich a display element such as an organic light emitting diode (OLED)panel or a plasma display panel is used, similar to the above-describedembodiment.

(2) While the image processing circuit 20 operates to output the pulseat a high level as the progress information P when one line of the imagedata of the display image is able to be output in the above-describeddescription, the pulse at a high level may be output as the progressinformation P when a predetermined number of lines (block unit) of thedisplay image is able to be output. In this case, the image outputcircuit 30 outputs the image data of the display image for apredetermined number of subsequent lines (block unit) to the EVFcontroller 40 in synchronization with the horizontal synchronizationsignal according to the progress information P and then, waits for thepulse at a high level to be supplied as the progress information P.Further, the pulse at a high level may be output as the progressinformation P when the display image for units of blocks is able to beoutput as units of blocks using a half of one line or a predeterminedarea as units of blocks.

(3) While the enable signal DE that becomes active when the image signalDgb is a valid image signal and becomes inactive when the image signalDgb is an invalid image signal has been described as an example of thecontrol signal in the above-described embodiment, the present inventionis not limited thereto. For example, a disable signal that becomesactive when the image signal Dgb is an invalid image signal and becomesinactive when the image signal is a valid image signal may be used. Thatis, a control signal indicating that the image signal Dgb is valid orinvalid may be used.

Further, while the processing time of the image processing in the imageprocessing circuit 20 is variable in the above-described embodiment, thepresent invention is not limited thereto and the processing time may befixed. Even in this case, the delay time can be gradually shortened andthe synchronization can be performed with precision in units ofhorizontal synchronization periods even when the delay time of theoutput of the image sensor 12 and the displaying of the EVF 50 is longby outputting the enable signal DE indicating that the image signal isvalid or invalid from the image output circuit 30 together with theimage signal Dgb using the progress information P.

(4) While the data transmission between the image output circuit 30 andthe EVF controller 40 is performed using the parallel I/F (D00 to D23)in the above-described description, the data transmission may beperformed using a serial I/F of low voltage differential (LVDS). In thiscase, for example, an LDVS I/F 34 and an LDVS I/F 46 are provided in theimage output circuit 30 and the EVF controller 40, respectively, asillustrated in FIG. 15.

The LDVS I/F 34 includes a 7-multiplication PLL circuit 34 a that7-multiplies the second dot clock DCLK, a serial converter 34 b thatconverts image data (parallel) of the display image from the data outputcontrol unit 31 into a serial signal, and a data transmission circuit 34c that transmits the image data subjected to serial conversion. Further,the LDVS I/F 46 includes a 7-multiplication PLL circuit 46 a that7-multiplies a received clock, a data reception circuit 46 b thatreceives image data (serial) from the data transmission circuit 34 c,and a parallel converter 46 c that converts the received image data(serial) of the display image into a parallel signal and supplies theparallel signal to the data input unit 41.

Between the LDVS I/F 34 and the LDVS I/F 46, the verticalsynchronization signal DVsync (VS), the horizontal synchronizationsignal DHsync (HS), the data enable signal DE, and the image data Dgb(D00 to D23: 8 bits of RGB colors; R0 to R7, GO to G7, and BO to B7) aretransmitted, for example, as a serial signal for 4-differential inputand output in synchronization with a clock INCLK, as in FIG. 16 (JEIDAscheme) or FIG. 17 (VESA scheme). Further, in FIG. 15, the image dataLD00 to LD23, the data enable signal LDE, the second horizontalsynchronization signal LHsync, and the second vertical synchronizationsignal LVsync are described so as to distinguish signals and databetween after LDVS transmission and before the transmission, but thesecorrespond to the image data D00 to LD23, the data enable signal DE, thesecond horizontal synchronization signal DHsync, and the second verticalsynchronization signal DVsync, respectively.

The same operation and effects as those in the above-describedembodiment can be achieved even when transmission of image data of thedisplay image or the like is performed between the image output circuit30 and the EVF controller 40 using such an LDVS I/F.

(5) While the value of the register 43 a is transmitted between theserial I/F 33 and the serial I/F 45 in the above-described description,the value may be transmitted as data (D00 to D23) in the period in whichthe data enable signal DE is inactive when the LDVS I/F is used asdescribed above.

(6) While the case in which the EVF is built in the imaging displayapparatus 1 has been described in the above-described description, theEVF controller 40 and the EVF 50 may be configured as, for example, afinder (display device) connected to the outside of a digital camera. Inthis case, the device may be an imaging device further including theimage output circuit 30.

(7) While the case in which the invention is configured as the imagingdisplay apparatus 1 has been described in the above-describeddescription, the present invention is not limited thereto and may beconfigured as, for example, electronic equipment (display device) suchas a projector device, a head up display (HUD), or a head mount display(HMD). Further, the present invention can be applied to, for example,electronic binoculars, electronic glasses, an electron microscope, afinder of medical electron glasses, an in-vehicle back monitor, or amonitor of an in-vehicle side-view mirror as long as they are displaydevices performing live view, and a delay from imaging to displaying canbe reduced. Further, in an aspect of the display device, the imagingunit 10 may not necessarily be included. That is, the image processingcircuit 20 to which the imaging data Ds is supplied, the image outputcircuit 30, the EVF controller 40, and the EVF 50 may be regarded as thedisplay device.

REFERENCE SIGNS LIST

-   1 Imaging display apparatus-   12 Image sensor-   20 Image processing circuit-   30 Image output circuit-   31 Data output control unit-   40 EVF controller-   41 Data input unit-   42 Counter-   43 Timing generation unit-   44 Data output unit-   50 EVF-   51 Liquid crystal panel-   52 Scanning line selection unit-   53 Data line driving unit.

1. An imaging device comprising: an imaging element that captures animage and outputs an imaging signal; an image signal output unit thatoutputs an image signal based on the imaging signal; and a controlsignal output unit that outputs a control signal indicating whether theoutput image signal is valid or invalid in synchronization with ahorizontal synchronization signal.
 2. The imaging device according toclaim 1, wherein a period of the horizontal synchronization signal isconstant, and the image signal includes an invalid image signal and avalid image signal, and either the invalid image signal or the validimage signal is output in synchronization with the horizontalsynchronization signal.
 3. The imaging device according to claim 2,wherein the control signal output unit outputs a control signalindicating that the image signal is the valid image signal when theimage signal is able to be output in synchronization with the horizontalsynchronization signal, and outputs a control signal indicating that theimage signal is the invalid image signal when the image signal is unableto be output in synchronization with the horizontal synchronizationsignal.
 4. The imaging device according to claim 2, wherein the imagesignal output unit includes an image processing circuit which performsimage processing of which processing time is variable on the imagingsignal, and outputs progress information indicating progress of theimage processing; and an image output circuit that determines whether asignal obtained through the image processing of the image processingcircuit is able to be output as the valid image signal insynchronization with the horizontal synchronization signal based on atleast the progress information, and outputs the valid image signal whena determination condition is positive and the invalid image signal whenthe determination condition is negative.
 5. An image processing devicecomprising: an image signal output unit that outputs an image signalbased on an imaging signal obtained by capturing an image; and a controlsignal output unit that outputs a control signal indicating whether theoutput image signal is valid or invalid in synchronization with ahorizontal synchronization signal.
 6. A display control devicecomprising: an input unit that inputs an image signal and a controlsignal indicating whether the image signal is valid or invalid insynchronization with a horizontal synchronization signal; and a displaycontrol unit that performs control to cause a valid image signal to bedisplayed on a display unit based on the control signal.
 7. The displaycontrol device according to claim 6, wherein a frame rate of the displayunit is higher than a frame rate of an imaging signal.
 8. An imagingdisplay apparatus comprising: the imaging device according to claim 2;the display control device according to claim 5; and a display unit thatdisplays an image.